Self-organized microgratings in LiNbO3 fabricated by a slit-shaped femtosecond laser for optical attenuation

•The method of preparing self-organized micro-gratings is slit shaped femtosecond laser directing writing.•The method of preparing self-organized micro-gratings can produce uniform self-organized micro-gratings with a period of 1.57 μm to 2.68 μm.•The maximum attenuation ratio of this self-organized micro-gratings based attenuator is about 45.7 % to 633 nm. Preparing multifunctional 3D microstructures in transparent materials, such as phase plates, light attenuators, and metasurfaces, is critical in science and technology. Here, the self-organized micro-gratings were created inside the z-cut LiNbO3 using slit-shaped femtosecond laser direct writing. The effects of the processing parameters and slit widths on the micro-grating’s formation are investigated. The Raman mapping, energy dispersive spectroscopy, and the micro polariscope are adopted to understand the general mechanism of periodic gratings’ generation. An optical attenuator with a spacing of 15 μm was fabricated to demonstrate the potential of micro-grating. The attenuator showed the max attenuation (about 45 %) at 633 nm, indicating the potential application of micro-gratings in optical information processing. The micro-gratings provide a pathway for expanding the applications of LiNbO3 and fabricating multifunctional photonic structures.